I worked in an office that overlooked a car repair/service/MOT place. The garage had one of those phones that had a ringer on the wall outside so the mechanics knew when the phone was ringing if they were in the yard. Some evenings when we were bored we would wait until the last guy was locking up and just as he had turned the key we would ring and wait for him to go back inside to answer the phone. Just as he was about to pick up we would hang up. We would then wait for him to go outside and start locking up again before ringing again to see how many times he would go back inside to answer. The record was 4 times.